In the design of modern integrated circuits, particularly digital circuits, standard cells having fixed functions are widely used. Standard cells are often pre-designed and stored in cell libraries. In some applications, a standard cell includes a group of transistor and interconnect structures that provide a Boolean logic function (e.g., AND, OR, XOR, XNOR, or INV), a storage function (e.g., flipflop or latch), or other predetermined functions. At the time integrated circuits (applications) are designed, the standard cells are retrieved from the cell libraries and placed into desirable locations. Routing is then performed to connect the standard cells with each other and with other customized circuits on the same chip. The overall area and power consumption of an integrated circuit thus depend on the area and power consumption of individual standard cells.